Suction muffler for a reciprocating hermetic compressor

ABSTRACT

A suction muffler for a small refrigeration system, the muffler including an enclosed equalizing chamber acting upon a tubular connector and a fluid communication between the equalizing chamber and an acoustic chamber. The assembly simultaneously minimizes the noises of gas pulses inside the suction muffler and the pressure differential between the inside and outside of the tubular connector.

FIELD OF THE INVENTION

The present invention refers to a suction muffler to be mounted at therefrigerant gas supply region in a reciprocating hermetic compressor,particularly in a reciprocating hermetic compressor of direct suctionused in small refrigeration systems.

BACKGROUND OF THE INVENTION

Reciprocating hermetic compressors have their suction provided with anacoustic dampening system (acoustic filters or suction mufflers)provided inside the shell and which conducts the gas coming from thesuction line to the suction valve.

This component executes several functions that are important to theadequate operation of the compressor, such as gas conduction, acousticdampening and, in some cases, thermal insulation of the gas that isdrawn to the inside of the cylinder.

The suction muffler generally consists of a sequence of volumes andtubes that conduct the gas coming from the suction line directly to thesuction valve. This gas displacement produces pulses, generating noisesthat are propagated in an opposite direction to the gas flow toward thesuction valve. The more efficient the suction muffler at its acousticoutlet, the lower will be said pulses.

Another important function of the suction muffler is to conduct the gasto the suction valve with the least possible heating, avoiding thermalexchanges with the gas stagnated inside the compressor shell and alsoreducing its contact with the hot parts inside the compressor. On theother hand, the suction muffler represents a load loss to the gas flowbeing drained. Its influence on the performance of the compressor ishighly important. The suction mufflers are mostly constructed in amaterial of low thermal conductivity and affixed to the compressor headthrough the cylinder cover. The dimensioning of the internal volumes ofthe suction muffler tubes determines, to a great extent, the efficiencyof the latter.

In some known constructions for the compressors of refrigerationsystems, the gas suction occurs by direct suction from the inlet tube tothe inside of the suction muffler. In these constructions, the suctionline is maintained in fluid communication with the suction mufflerthrough a flexible connector that conducts the cold suction gas directlyto the interior of the muffler, minimizing the thermal exchanges of thiscold gas with the gas stagnated inside the shell. This connection can beconstructed in a flexible material of low thermal conductivity andretained to the suction muffler and in a sliding contact with thecompressor shell, such as it occurs in the solution described in U.S.Pat. No. 4,793,775.

In this type of prior art construction, the flexible connector worksadequately during the normal operation of the compressor, directing thecold gas from the suction line to the suction valve, without submittingthis incoming gas flow to be mixed with the heated gas contained in thecompressor shell, and also minimizing the transfer, to the shell, of thenoises resulting from the gas pulses inside the suction muffler.

However, this known construction presents the inconvenience of notallowing the refrigeration system to rapidly and adequately return tothe pressure levels of the normal working regimen of the compressor,when the latter is driven after a stop period in which the pressureinside the shell is raised to a value of equilibrium with the suctionand discharge sides of the compressor.

When the compressor is re-started, the pressure inside the suctionmuffler and inside the flexible connector is suddenly reduced,originating a pressure differential that is greater than the stoppressure inside the compressor shell, causing a certain collapse of theflexible connector and the compressor assembly tilts toward the shell,compressing the flexible connector and submitting it to undesirableefforts as long as the strong pressure unbalance condition lasts betweenthe interior of the shell and the interior of the suction muffler. Sincethe latter is constructed, in case of the direct suction, to berelatively hermetically coupled to the inlet of the suction muffler andto the shell, the pressure inside the latter remains high in relation tothe interior of the suction muffler for a long period, during which theflexible connector remains resiliently deformed and inadequatelysubjected to undesirable efforts that tend to damage it or displace itfrom its operative position.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a suction mufflerfor a reciprocating hermetic compressor with direct suction, which doesnot present the inconveniences of the known prior art solutions,producing a fast and efficient equalization of the pressures existinginside the shell and inside the suction muffler, without submitting theelements of the direct suction to undesirable efforts and withoutcausing loss in the volumetric efficiency of the compressor.

It is another object of the present invention to provide a suctionmuffler as mentioned above, which produces a better attenuation of thenoises produced by the gas pulses inside the suction muffler.

It is a further object to provide a suction muffler, which, besides theabove characteristics, allows for a better fixation of the connector tothe gas inlet thereof.

SUMMARY OF THE INVENTION

These and other objects are achieved by a suction muffler for areciprocating hermetic compressor mounted inside a hermetic shell, saidsuction muffler comprising a hollow body that defines at least oneacoustic chamber and that is provided with a gas inlet connected to asuction line by means of a flexible connector, and with a gas outletconnected to a suction valve of the compressor, said suction mufflercomprising an equalizing chamber, which is provided, on one side, withan opening to the inside of the hermetic chamber and, on the other side,with a fluid communication with the acoustic chamber, said equalizingchamber and said fluid communication being dimensioned so as tominimize, simultaneously, the transfer of acoustic energy to the cavityof the shell, the mixture of said gas with that contained inside thehermetic shell, and the pressure differential between the inside of thelatter and the suction line, upon operation of the compressor after astop period.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below, with reference to the attacheddrawings, in which:

FIG. 1 shows, schematically, a longitudinal sectional view of acompressor presenting a direct suction between an inlet tube and asuction muffler, constructed according to the present invention, using aconnector affixed to said suction muffler;

FIG. 2 shows, schematically and in a longitudinal sectional view, thesuction muffler in FIG. 2 mounted inside the hermetic shell of thecompressor;

FIG. 3 shows, schematically and in an exploded perspective view, thesuction muffler of the present invention and a connector to be affixedto an inlet thereof, when in the mounting condition; and

FIG. 4 shows, schematically and in a longitudinal sectional view, thesuction muffler of the present invention, presenting the connectorseated on the hermetic shell and opened to the interior of the suctionmuffler conducting tube.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

The present invention will be described for a compressor of the typeused in refrigeration systems and comprising: inside a hermetic shell 1,a motor-compressor assembly having a cylinder block where is defined acylinder 2 lodging, at one end, a reciprocating piston 3, and having anopposite end closed by a cylinder cover 4 defining therewithin a housing5 for adaptation of the suction muffler, and a discharge chamber 6 (FIG.3) in selective fluid communication with a compression chamber 7 definedinside the cylinder 2 between a top portion of the piston 3 and a valveplate 8 provided between the opposite end of the cylinder 2 and thecylinder cover 4, through suction orifices 8 a and discharge orifices(not illustrated), which are provided on said valve plate 8 andselectively respectively closed by suction valves 8 b and dischargevalves (not illustrated).

According to the illustrations, the gas drawn by the compressor andcoming from a suction line 9 of the refrigeration system and opened tothe inside of the hermetic shell 1, reaches the latter through an inlettube 9 a affixed to the external side of said hermetic shell 1 and whichis in fluid communication with the suction muffler mounted inside saidhermetic shell 1, through a tubular connector 10 of flexible material,said suction muffler being mounted in the housing 5 in fluidcommunication with the suction valve 8 b of the valve plate 8.

As illustrated in the enclosed drawings, the suction muffler of thepresent invention comprises a hollow body 20, which is generallyobtained from a material of low thermal conductivity and presents arectangular cross section, for example, and which is closed by an uppercover 30 to be seated onto the upper edge of the hollow body 20 andthere affixed by any adequate means, such as for example, a pair ofclamps 40 that are fitted, by elastic deformation, into respective ears21 and 31 provided in the hollow body 20 and in the cover 30.

According to the present invention, the tubular connector 10incorporates, at one end 11, a first peripheral flange 12 that is seatedand retained inside the hollow body 20 by joining respective portions ofthe latter and of the upper cover 30 and, at an opposite end 13, asecond peripheral flange 14 that is seated against the internal face ofthe hermetic shell 1 concentrically with the suction line 9.

The hollow body 20 is provided with a gas inlet 22 in fluidcommunication with the gas supply to the compressor and which is alignedto the suction inlet tube 9 a of the suction line 9, and with a gasoutlet 32 in fluid communication with a suction side of the compressorand connected to the suction valve 8 b of the compressor. In theconstruction being described, the gas inlet 22 is defined by thejunction of the hollow body 20 and the upper cover 30, and the gasoutlet takes the form of a tubular extension that is superiorly andexternally incorporated to the cover 30 and has a free end configured tobe adapted to the suction orifice 8 a of the valve plate 8 of thecylinder cover 4 of the hermetic compressor.

According to the present invention, the hollow body 20 defines, in theinterior thereof, at least one, for example two acoustic chambers, whichare separated from each other by a common wall portion defined by adividing plate 24 provided inside said hollow body 20, as describedahead.

The present suction muffler comprises a first acoustic chamber 25 influid communication with the gas outlet 32 of said hollow body 20, and asecond acoustic chamber 26 in fluid communication with the gas inlet 22of the suction muffler, said first and second acoustic chambers 25, 26being separated from each other by the dividing plate 24.

According to the illustrations, the hollow body 20 is provided, in alower wall 20 a, with a restricting orifice 27 by which the lubricantoil flows down and which is dimensioned to allow the passage of oilonly, avoiding the heated oil existing inside the shell 1 from reachingthe interior of the suction muffler and increasing the temperature ofthe gas therein.

The present suction muffler further presents a conducting tube 50 havinga first end 51 opened to the gas outlet 32 of the hollow body 20, and asecond end 52 opened to the gas inlet 22 of the hollow body 20, saidconducting tube 50 presenting median portions that are respectivelyopened to the first and the second acoustic chambers 25, 26 of thehollow body 20. The conducting tube 50 presents at least one window 54opened to the first acoustic chamber 25 and through which is effectedthe direct fluid communication between said first acoustic chamber 25and the gas outlet 32 of the hollow body 20, and also at least onewindow 53 opened to the second acoustic chamber 26 of the hollow body 20and through which is effected the direct fluid communication between thesecond acoustic chamber 26 and the gas inlet 22 of the hollow body 20.In the illustrated construction, the conducting tube 50 has two piecesand carries, on one of these pieces, the dividing wall 24 that definesthe separation between the first and the second acoustic chambers 25,26.

According to the present invention, the hollow body 20 presents,internally, an equalizing chamber 60, which is provided, on one side,with an opening 60 a to the inside of the hermetic shell 1 and, on theother side, with a fluid communication 61 having an acoustic chamber,said equalizing chamber 60 and said fluid communication 61 beingdimensioned to minimize, simultaneously, the noises from the gas pulsesinside the suction muffler, the mixture of said gas with that containedinside the hermetic shell 1, and the pressure differential between theexterior of the hermetic shell 1 and the suction line, upon operation ofthe compressor after a stop period.

The equalizing chamber 60 is dimensioned to have only one portion of itsinternal volume defined adjacent to the fluid communication 61, whichportion is alternatively filled with the gas coming from the acousticchamber, particularly from the first acoustic chamber 25, and onlyfilled with the gas coming from the remaining internal volume of theequalizing chamber 60 upon operation of the compressor. Thus, the gascontained in the hermetic shell 1 cannot reach the interior of theacoustic chamber through the fluid communication 61 during the normaloperation of the compressor. Said internal volume of the equalizingchamber 60 presents a cross section that coincides with the crosssection of the equalizing chamber 60 along the extension of saidinternal volume portion.

According to the illustrations, the equalizing chamber 60 presents anelongated shape, with an end opened to the acoustic chamber, and anopposite end opened to the interior of the hermetic shell 1, the openingof the equalizing chamber 60 to the interior of the hermetic shell 1presenting a contour that coincides with that of the equalizing chamber60 at the region of said opening.

According to the present invention, the fluid communication 61 isprovided adjacent to the gas outlet 32 of the hollow body 1 and it isdefined, for example, by an orifice provided in a wall that is common toboth the acoustic chamber and the equalizing chamber 60.

1. A suction muffler for a reciprocating hermetic compressor mountedinside a hermetic shell, said suction muffler comprising: a hollow bodydefining at least one acoustic chamber, said at least one acousticchamber having a lower wall provided with a restricting orifice fordraining oil; the hollow body being provided with a gas inlet connectedto a suction line by means of a tubular connector and a gas outletconnected to a suction valve of the compressor; the hollow body furthercomprising an equalizing chamber having an opening to the interior ofthe hermetic shell on one side, and a fluid communication with theacoustic chamber on the other side; wherein said equalizing chamber hasan elongated shape and an internal volume with a cross section that issubstantially uniform along the extension of said internal volume, thefluid communication being defined by a second orifice provided adjacentto the gas outlet of the hollow body, said second orifice being disposedin a wall different from the lower wall of the hollow body and common toonly the acoustic chamber and the equalizing chamber; wherein theequalizing chamber and said second orifice are dimensioned to preventgas contained inside the hermetic shell from entering the acousticchamber, said equalizing chamber having only one portion of its internalvolume, defined adjacent to the second orifice, alternatively filledwith the gas coming from the acoustic chamber and with the gas comingfrom the remaining internal volume of the equalizing chamber upon normaloperation of the compressor; wherein said equalizing chamber openingbeing dimensioned to allow said remaining internal volume of theequalizing chamber to be filled with gas from the inside of the hermeticshell; and wherein the equalizing chamber and said second orifice arealso dimensioned to minimize the noises from the gas pulses inside thesuction muffler, the mixture of said gas with the gas contained withinthe hermetic shell, and the pressure differential between the exteriorof the hermetic shell and the suction line, upon operation of thecompressor after a stop period.
 2. The suction muffler as set forth inclaim 1, wherein the hollow body defines, internally, first and secondacoustic chambers and a conducting tube with its opposite endsrespectively connected to the gas inlet and the gas outlet of the hollowbody, and with median portions respectively opened to the first and thesecond acoustic chambers, the first acoustic chamber being adjacent tothe gas outlet of the hollow body.
 3. The suction muffler as set forthin claim 1, wherein the tubular connector is in a flexible material andincorporates, at one end, a first peripheral flange that is seated andretained inside the hollow body and, at an opposite end, a secondperipheral flange seated against the internal face of the hermetic shellconcentrically with the suction line.
 4. The suction muffler as setforth in claim 3, wherein the gas inlet is formed by the junction of thehollow body with an upper cover, said first peripheral flange beingretained by respective portions of the hollow body and of the uppercover.
 5. The suction muffler as set forth in claim 1, wherein the fluidcommunication is separate from the gas inlet.